Characteristic Behavior of Lithium and Magnesium Perchlorate Salts in Binary Organic System Followed Conductometrically

The conductivity of lithium and magnesium ions in mixed electrolyte systems of 1, 2-dimethoxyethane (DME) and ethylene carbonate (EC) was investigated. The organic electrolyte solutions were prepared by mixing varied volume ratios of DME and EC with varying concentrations of lithium and magnesium perchlorate salts. The conductivities, cell voltages and Gibbs free energy of the redox reaction were determined. Comparing the molar conductivities of these two salts measured at 25 oC in the mixed DME-EC system, 0.5M Mg(ClO4)2 gave more molar conductivity of 28.68 mScm-1 against 26.85 mScm-1 of LiClO4. However, at relatively higher concentrations (1.0M and 2.0M), LiClO4 yielded better molar conductivity results than Mg(ClO4)2. Cell voltage was highest in the Mg(ClO4)2-DME-EC system with a value of 0.87 volts and 0.74 volts for LiClO4-DME-EC system. The negativity of Gibbs free energy was also highest for Mg(ClO4)2-DME-EC (-167.910 kJ/mol at 40 % DME), while that of LiClO4-DME-EC was -71.410 kJ/mol at 60 % DME. This indicates greater spontaneity of Mg(ClO4)2-DME-EC cell reaction. The mixing ratio of the DME-EC system for optimum battery performance was resolved to be 60 % DME for LiClO4 salt and 40 % DME for Mg(ClO4)2 salt. The interpretations of experimentally deduced results were based on the influence of ion-solvent and solvent-solvent interactions in the DME-EC system.